The ability to classify vehicles quickly and efficiently is needed in a number of transportation and security applications, and laser scanner sensors have been employed for such vehicle classification. In general, laser scanners are measuring devices that emit pulses of light towards objects. These devices can, for example, detect the part of the light that is reflected from the objects, measure the time difference between emission and reflection, and derive a distance to the object. The operation can be repeated for a varying set of angles. Scanners can be placed overhead of passing traffic to capture top views, on the side passing traffic to capture side views, facing traffic to capture front views, and/or a combination thereof.
Laser scanners are a common type of equipment for vehicle classification. For example, laser scanners can be used for determining the vehicle type in tolls. However, this is usually achieved by simple solutions such as extracting a few high-level features and classifying them (sometimes with simple rules), or matching the raw laser profiles.
As an example, some systems have been developed for vehicle classification, which extract the following features from a laser scan: width, height, length, number of vehicle units, and height of the first unit. Using this approach, vehicles can be classified using simple rules comparing feature values with pre-specified thresholds. While such an approach might provide initial satisfactory performance, it is limited in scope and efficiency, requires intense human labor and expertise, and lacks learning classification capabilities
Accordingly, laser scanning technologies may benefit from proved techniques of classifying vehicles from the results of the scan.